but what about all this obsession about ensuring that there are still humans in say 200 years, when anyone who might exist is a complete stranger to us?
Because people care about their grandchildren/future family? I honestly can't understand this question. You can see it around you everywhere. Wealthy families even ensure that generations down the line will have some wealth. People give heaps of money to charity to help other people they will never know. People just care about other people even if they don't necessarily know them directly.
and yet most humans continue pursuing a lifestyle that is simple not sustainable at an 8 billion people scale, and don't want to give it up. Doesn't sound like they care much about the consequences of their actions on others.
Haven't made the calculations, but I'm quite sure we could keep the current technological pillars of well-being (food, health, heating) without much issue to the environment if we gave up all the other superfluous crap (private cars, gadgets, plastics toys, 3d videogames, etc). And we'd probably be much less depressed too.
I agree there will probably be a mass die off of humans in the coming century as resources dry up and wars erupt over said resources (exacerbated by climate change) but it doesn't mean we have to give up